Segmented abrasive rim disc and method for making the same



July 7, 1964 R. J. WALTERS 3,139,709

SEGMENTEID ABRASIVE RIM DISC AND METHOD FOR MAKING THE SAME Filed April15, 1965 INVENTOR Rev J. WALT 5R5 BYJWMW ATTORNEY United States Patent3,139,709 SEGMENTED ABRASIVE RIM DISC AND METHOD FOR MAKING THE SAME 7Roy J. Walters, 4985 Voltaire St., San Diego, Calif. Filed Apr. 15,1963, Ser. No. 272,989 2 Claims. (Cl. 51-195) This invention relates toan improvement in abrasive rim discs for use with edge grinders and to amethod of making the same.

In particular this invention is an improvement of the abrasive rim discand the method of its manufacture disclosed in my co-pendingapplication, Serial No. 16,587, filed on March 21, 1960, now abandoned,which broadly concerns the bonding of an abrasive particle covered ringor rim piece to the peripheral face portion of a plain uncoated fiberbacking disc and the method of manufacturing such abrasive rim portions.The method therein disclosed consists of cutting circular rim portionsof rings from a sheet of abrasive covered roll stock, or of cutting suchcircular rim portions from used conventional discs of larger diameter.The advantage of the rim disc of the above mentioned application as wellas one of the advantages of the present invention resides in theapplication of abrasive material only to those portions of the backingdisc which are actually used in grinding. The conventional abrasivediscs used with edge grinding prior to my invention consisted of a fiberbacking disc completely covered with abrasive particles.

The principal object of the present invention is to pro vide anabrassive rim disc having improved flexibility and improved abrasivecharacteristics and life when it is used on painted and other softsurfaces.

A further object is to provide an improved economical method ofmanufacture of abrasive rim discs.

These objects are attained by an abrasive rim disc which does not have auniform abrasive covering over the entire face portion as thosegenerally employed heretofore, but which is made from an abrasivecovered strip with transverse slits which is adhered to a backing discto provide segments of abrasive material separated by generallytransverse gaps or grooves. Such grooves provide greater flexibility tothe disc at its cutting edge and thus aid in avoiding gouging of thework piece. In addition the discs performance and life, when used onpainted or other soft surfaces, is greatly improved because the softsubstance does not remain on the abrasive crystals and impairs theircutting ability but is removed by the grinder action and is accumulatedin the gaps between the segments.

The novelty of the method of manufacture of the above described abrasiverim disc lies in the fact that the abrasive rim portion is manufacturedfrom a straight strip of abrasive covered material. In View of the factthat generally the same width of abrasive material is required or usedon the rim of a disc regardless of its diameter, the same width stripmay be employed in the manufacture of a complete line of abrasive rimdiscs. This method also does not involve any by-product in the form ofscrap or trimmings since the entire strip is used in providing theabrasive surface to the disc. In practice it has been found that a oneinch wide strip may be used in manufacture of discs ranging from over 8"to 2" in diameter.

The present method is a significant step forward over the methoddisclosed in the above mentioned co-pending application whichcontemplated the cutting of concentric rings from a sheet to provide theabrasive rim portions for discs of progressively smaller diameters,since the latter method invariably limits the manufacturer to producingequal number of discs of the various sizes re 3,139,709 Patented July 7,1964 gardless of the variance in the sales volume or popularity of onesize over the other.

Other objects and advantages will be apparent from, or pointed out in,the specification and the appendant claims, as will obviousmodifications of the single embodiment shown in the drawings, in which:

FIG. 1 is a cross sectional side View of a rim disc mounted on a back-uppad connected to a power tool mandrel;

FIG. 2 is a fragmentary top view of a strip of abrasive coated materialwhich is prepared to be bonded to backing disc; and

FIG. 3 is a front view of the abrasive rim disc.

The abrasive rim disc embodying my invention is manufactured byproviding a substantially straight strip 10 of abrasive coveredmaterial, slitting the same at 12 to provide a plurality of separateequally spaced segments 14 connected by a relatively narrow neck portion18 along one side of the strip, bending the strip to a flat ring shape,and bonding the same to the peripheral portion of the face of a backingdisc 18 with the unitary side of the strip forming the inside of thering and the segments flaring out to form gaps 20 between the separatesegments.

The strip 10 may be cut to the exact finally utilized length from a coilof abrasive coated material equal in width to the required width of thestrip, thereby eliminating practically all trimming and other waste ofmaterial. The strip material may be abrasive coated paper, cloth orfiber which are well known in the art.

As seen in FIG. 3, the abrasive rim disc manufactured pursuant to theabove described method comprises an uncoated fiber backing disc 18having its peripheral face portion provided with an abrasive rim 22 of awidth equal to or slightly larger than that disc portion which isactually used in the use of the disc.

The backing disc 18 has an aperture 21 sized to pass the shank 24 of thehead nut 26 and small enough so that the head 28 of nut 26 will not passthrough the aperture. Nut 26 has several internal threads 30 sized toreceive threaded power tool mandrel 32. The nut is tightened to themandrel to secure the backing disc 18 to the back-up pad 34 and seats ina counter sunk portion 36 of the pad to prevent the head 28 fromcontacting the work surface.

There are a number of applications in which it is desirable that thebacking disc and its abrasive covered portion flex during sanding. Forsuch uses the back-up pad 34 is of substantially smaller diameter thanthe abrasive rim disc. Due to its serration the segmented rim discprovides uninhibited flexing of the backing disc 18 and actually exertsmore flexing than the conventional coated fiber disc. This free flexingexposes and employs more than the usual number of the abrasive crystalsto the surface being sanded which results in a substantially fastercutting action and longer disc life.

Although but one embodiment of the present invention has beenillustrated and described, it will be apparent to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the spirit of the invention or from the scope of theappended claims.

I claim:

1. An abrasive rim disc comprising, a flexible backing disc adapted tobe attached to and rotated by a power tool, a flat strip bent to a flatring shaped form and having one of its faces bonded to the peripheralportion of the face of said backing disc and having the other of itsfaces covered with abrasive material, said strip being unitary on theinner radial side of said disc and forming a plurality of spaced apartsegments on the outer radial side of said disc to thereby form aplurality of grooves I 3 each of them defined by two of said segmentsand said backing disc.

2. A method of manufacturing an abrasive rim disc comprising the stepsof: partial transverse slotting of a substantially straight strip ofmaterial which has one of its faces coated with abrasive materialthereby dividing said strip into a plurality of segments connected by aunitary portion, and bonding the other face of said strip to theperipheral portion of the face of a backing disc in a manner wherebysaid strip assumes a flat ring shaped form and said unitary portiondefines the inner portion of said ring shaped form and the segmentsspread apart References Cited in the file of this patent UNITED STATESPATENTS 302,952 Smith Aug. 5, 1334 888,129 Tone May 19, 1903 1,216,489Pfeifier Feb. 20, 1917 10 2,334,642 Moore Nov. 16, 1943 2,677,142 MundoMay 4, 1954

1. AN ABRASIVE RIM DISC COMPRISING, A FLEXIBLE BACKING DISC ADAPTED TOBE ATTACHED TO AND ROTATED BY A POWER TOOL, A FLAT STRIP BENT TO A FLATRING SHAPED FORM AND HAVING ONE OF ITS FACES BONDED TO THE PERIPHERALPORTION OF THE FACE OF SAID BACKING DISC AND HAVING THE OTHER OF ITSFACES COVERED WITH ABRASIVE MATERIAL, SAID STRIP BEING UNITARY ON THEINNER RADIAL SIDE OF SAID DISC AND FORMING A PLURALITY OF SPACED APARTSEGMENTS ON THE OUTER RADIAL SIDE OF SAID DISC TO THEREBY FORM APLURALITY OF GROOVES EACH OF THEM DEFINED BY TWO OF SAID SEGMENTS ANDSAID BACKING DISC.